1. Field of the Invention
The invention concerns a method and an apparatus for generation of an x-ray image of the female breast.
2. Description of the Prior Art
In x-ray mammography, a two-dimensional x-ray image of the female breast is generated. During the x-ray image acquisition, the breast is located between two compression plates, of which the compression plate associated with an x-ray source is permeable for the x-ray radiation that is used. A planar x-ray receiver, for example an x-ray film or a digital image transducer device, is located on the opposite compression plate. The x-ray beam used in the exposure, originating approximately from a point, is dimensioned such that it irradiates the entire reception surface of the x-ray receiver. The tissue appearing light on the x-ray image is then completely surrounded by an over-exposed (i.e. dark) area, and the evaluation of the x-ray image is made easier. However, this has the consequence that not only the breast but also the surrounding tissue recorded by the x-ray beam are irradiated. This does not lead directly to an increased radiation exposure of the breast; however, due to scattering on the compression plates, x-ray radiation is generated that can both disadvantageously influence the image quality and indirectly lead to an increased radiation exposure of the patient or the operating personnel. Given the use of an x-ray film as an x-ray receiver, the size of the film (and thus the necessary cross-sectional area of the x-ray beam) can be simply adapted to the current anatomical conditions by selection of a matching film format. This is not possible in x-ray mammography apparatuses in which a relatively costly digital image transducer device is used as the x-ray receiver, such that the entire reception surface of the x-ray receiver is exposed when the dimensions of the breast located between the compression plates are significantly smaller than the dimensions of the reception surface (and thus of the x-ray beam used).